Nitroalcohol phosphate curing catalyst for aminoplasts



aminoplastic resins.

Patented May 20, 1952 NITROALCOHOL PHOSPHATE CURING CATALYST FORAMINOPLASTS Herbert J. West, Pittsburgh, Pa., assignor to AmericanCyanamid Company, New York, N. Y.,

a corporation of Maine No Drawing. Original application November 8,

1946, Serial No.'708,810. Divided and this application September 29,1950, Serial No. 187,675

14 Claims. 1

This invention relates to aminoplastic coating compositions havingcuring accelerators incorporatedtherein, and more particularly, it isdirected to nitro aliphatic esters of phosphoric acids incorporated inaminoplastic compositions to accelerate the cure thereof.

Nitro'aliphatic esters of phosphoric acids contain two catalyzingnuclei, and therefore more rapidly accelerate the cure of aminoplastics.These esters may be prepared by reacting a phosphoric acid with a nitroderivative of an alcohol capable of forming an ester therewith. Suitablealcohols are the nitro derivatives of ethanol, butanol, propanol, andthe like. These alcohols, or a mixture thereof, may be reacted withphosphoric acids and phosphorous pentoxide, preferably, atsubatmospheric temperatures in the presence of 'an inert diluent such asbenzene, xylene, and the like, to obtain nitro aliphatic esters ofphosphoric acids.

Catalysts prepared in this manner may be used to accelerate the curingrate of all types of clear and pigmented coating compositions containingSince aminoplastic resins generally cure to a relatively brittle film,it has been found advantageous to blend with the aminoplastic coatingcompositions, an alkyd resin which is oil-modified to effectcompatibility. Likewise, it is preferable to prepare these coatingcompositions with an alkylated aminoplastic resin. For example, coatingcompositions prepared from an alkylated urea or alkylated melamine resinor a mixture thereof, is blended with an oil-modified alkyd resin to:produce an eflicient coating composition.

When a coating composition of the urea-formaldehyde type is blended with0.25.0% of a nitro aliphatic polyphosphoric acid ester, tough coatingsurfaces or films are obtained within one to two hours at a temperatureof 120-1l0 F. These aminoplastic coating compositions containing theseaccelerators have been found to dry to an insoluble film within 24.hours at room temperature. The melamine-formaldehyde coatingcompositions require higher temperatures for accelerated cure,preferably above 200 F. These accelerators are particularly useful inaccelerating the cure of coating composition applied as wood finishes,because low drying temperatures are required in this industry.Previously strong mineral acids have been employed for this purpose, butwere found to give unstable solutions. The solutions containing thes newaccelerators are relatively stable. They are also of particular valueinbaked enamel compositions, as they substantially reduce the curing timeat elevated temperatures.

The following examples illustrate procedures suitable for thepreparation of accelerators of the type employed in this invention.

Example 1 parts of 2 nitro l butanol were placed in a suitable reactionvessel equipped for mechanical agitation or stirring. Into this alcoholthere was slowly poured, accompanied by vigorous stirring, a slushprepared from 89 parts of phosphorus pentoxide and parts of toluene. Themixture was vigorously stirred for four hours at room temperature.Immiscible layers were formed. These layers were separated. The lowerlayer was a very dark brown, viscous liquid.

Suitable accelerators have been prepared wherein the molar equivalent ofa nitro alcohol to phosphorous pentoxide has varied from 1:1 to 3:1.Likewise, suitable accelerators are provided employing orthophosphoricacid, metaphosphoric acid and pyrophosphoric acid instead of phosphoruspentoxide. These phosphoric acids and polyphosphoric acids are thenreacted with various nitro alcohols such as 2-nitro-2-methylpropanol,and Z-nitro butanol, 2-nitro-l-ethanol and the like. Any suitable inertdiluent such as benzene, toluene, xylene, and the like may be employedas a reaction medium.

Example 2 A mixture comprising 14.2 parts of phosphorus pentoxide and 62parts benzene were slowly added to 23.8 parts of 2-nitro-2-methyl-lpropanol while stirring. The temperature was maintained below 40 C., byoccasionally cooling in an ice bath.

' After several hours of stirring, the solid was completely dissolved,but two liquid phases were produced. The addition of 2 cc. of dioxane,destroyed the im'miscibility of the liquids and made it a homogeneoussolution.

In the preparation of suitable coating compositions, the following aminoresin dispersions were prepared.

1340 parts of butanol were added and the mixture heated to reflux andheld for one hour at reflux. 1550 more parts of butanol were added andthe mixture distilled with replacing feed of dry butanol until a batchtemperature of 112 C. was reached. The batch was then vacuumconcentrated at 90 C. to approximately 65% resin solids. This solutionwas diluted with xylene and butanol to give a final composition ofxylene, butanol and resin solids.

This resin solution was prepared in the manner described for thepreparation of solution A with the exception that approximately 4070parts of 37% formaldehyde solution were employed with the 1200 parts ofurea.

One mol of phthalic acid, 0.44 mol of soya fatty acids, and 1.06 mols of100% glycerine were heated to 220 C. and held for a sufficient period oftime to control acid number and viscosity, 8 hours usually beingsufiicient. This reaction product was diluted with xylene to give adispersion containing resin solid.

This resin solution was prepared by heating to 220 C. and holding atthis temperature for 4 hours, a mixture of 1.0 mol of phthalic acid,0.56 mol of soya fatty acids, and 1.0 mol of 100% glycerine. Thisreaction mixture was diluted with xylene to obtain a dispersioncontaining resin solids.

One mol of phthalic acid, 0.16 mol castor oil,

0.99 mol of 100% glycerine were heated at 280 C. r

for 45 minutes followed by a reduction of the temperature to 220 C., atwhich temperature it was held for three hours. This reaction product wasdiluted with xylene in sufficient quantity to obtain a dispersioncontaining 50% resin solids.

One mol of phthalic acid, 0.3 mol of linseed fatty acids, and 1.06 molsof 100% glycerine were heated at 220 C. for three hours. This reactionproduct was then diluted with xylene in sufficient quantity to obtain adispersion containing 40% resin solids.

This resin was prepared by effecting the adjunct of 0.6 mol of analpha,beta unsaturated dicarboxylic acid with 1 mol of a wood or gumrosin by heating to 2l0-240 C.

The following examples illustrate the coating composition formulationsand results obtained by employing accelerators of the type described inthis invention.

Example 3 To a surfacing composition comprising approxi- 4 mately 67parts of resin dispersion A and 33 parts of resin dispersion D, one partof nitro butyl phosphate was added. This coating composition was thenapplied to automotive steel panels and cured for 5 minutes at 250 F. Ahard, tough, water-resistant finish was obtained.

Example 4 To a, coating composition, prepared by blending approximately75 parts of resin dispersion A and 25 parts of resin dispersion D, andadjusting said blend with xylene to obtain a dispersion containing 41%resin solids, there was added 1 part of the reaction product obtained byreacting 2 mols of 2-nitro-1-methyl-1propanol with 1 mol of phosphoruspentoxide. This coating composition or dispersion was flowed ontoseveral panels of automotive steel immediately after the addition of theaccelerator. The coated steel panels were cured for various periods atvarious temperatures as follows: 24 hours at 78 F.; and 5 minutes at 250F. In all cases, tough, clear, hard surfaces were obtained.

Example 5 To a coating composition, prepared by blending approximately75 parts resin dispersion C and 25 parts of resin dispersion D anddiluting the blend with xylene to effect a coating compositioncontaining 42.5% solids, there was added nitro butyl ester ofpyrophosphoric acid in amounts varying from 1-5 parts. Thesecompositions were applied to automotive steel panels, some of whichwhere heated for 1 hour at 150 F., and others for 10 minutes at 200 F.,and the remainder for 5 minutes at 250 F. In all cases, tough, glossy,finishes were obtained. Better results were obtained, however, with thecompositions containing approximately 2.5 parts of accelerator p5erparts resin dispersions when cured at 2 0 F.

Example 6 To a white enamel, prepared with 50 parts titanium oxidedispersed in a blend of 35 parts of resin dispersion A and 65 parts ofresin dispersion D and adjusted with xylene to effect a dispersioncontaining approximately 55% non-volatile, there was added 1 part of thecatalyst prepared by Example 1. This coating composition was sprayed onsteel panels, and cured for 5 minutes at 250 F. Tough, hard lustrous,white finishes were obtained.

Example 7 To a white enamel, prepared by dispersing 50 parts titaniumoxide in a blend of 25 parts resin dispersion C and 75 parts resindispersion D and adjusted with xylene to efiect a dispersion containing67 parts non-volatile, there was added 2 parts accelerator prepared byExample 2. Metal panels coated with this composition and cured for 5minutes at 250 F. exhibited tough, glossy, hard finishes.

Example 8 50 parts of resin dispersion B, 40 parts of resin dispersionE, 10 parts of resin H, and 1.4 parts of accelerator prepared by Example2, were blended and the resulting coating composition sprayed ontofilled wooden panels. These panels were heated for two hours at F.,removed, and after light sanding, were given another coat, and baked for2 hours at 125 F. Excellent finishes were obtained which could be rubbedand polished an hour after final baking. These panels type disclosed asresin H with a blend of the other resins. The accelerators of the typedescribed hereinabove, have been found to possess utility with all thesecombinations.

The accelerators described herein are particularly useful withaminoplastic coating compositions. However, the illustrations givenherein above, are solely for the purpose of describing the invention,and are not to be considered in any way as a limitation upon theinvention.

This application is a division of application, 4

Serial No. 708,810, filed November 8, 1946, now Patent No. 2,526,179,

I claim:

1. A coating composition comprising a thermosettingmelamine-formaldehyde resin and a nitroaliphatic acid ester ofphosphoric acid having only nitro and phosphoric catalytic reactivesubstituents.

2. A coating composition comprising a thermosettingmelamine-formaldehyde resin and a nitroaliphatic acid ester ofpolyphosphoric acid having only nitro and phosphoric catalytic reactivesubstituents.

3. A coating composition comprising a thermosettingmelamine-formaldehyde resin and a ni-,

troalkyl acid ester of phosphoric acid having only nitro and phosphoriccatalytic reactive substituents.

4. A coating composition comprising a thermosettingmelamine-formaldehyde resin and a nitroalkyl acid ester of phosphoricacid having only nitro and phosphoric catalytic reactive substituents,said alkyl radical containing 2-4 carbon atoms.

5. A coating composition comprising a thermosettingmelamine-formaldehyde resin and a nitrobutyl acid ester of phosphoricacid having only nitro and phosphoric catalytic reactive substituents.

6. A coating composition comprising a thermosettingmelamine-formaldehyde resin and a nitropropyl acid ester of phosphoricacid having only nitro and phosphoric catalytic reactive substituents.

7. A coating composition comprising a thermosetting alkylatedmelamine-formaldehyde resin, a compatible alkyl resin and anitroaliphatic acid ester of phosphoric acid having only nitro andphosphoric catalytic reactive substituents.

8. A coating composition comprising a thermosetting alkylatedmelamine-formaldehyde resin, a compatible alkyd resin and a nitroalkylacid ester of phosphoric acid having only nitro and phosphoric catalyticreactive substituents.

9. A coating composition comprising a thermosetting alkylatedmelamine-formaldehyde resin, 2. compatible alkyd resin and a nitroalkylacid ester of phosphoric acid having only nitro and phosphoric catalyticreactive substituents, said alkyl radical containing 2-4 carbon atoms.

10. A coating composition comprising a thermosetting alkylatedmelamine-formaldehyde resin, a compatible alkyd resin and a nitrobutylacid ester of phosphoric acid having only nitro and phosphoric catalyticreactive substituents.

11. A coating composition comprising a thermosetting alkylated melamineformaldehyde resin, a compatible alkyd resin and a nitropropyl acidester of phosphoric acid having only nitro and phosphoric catalyticreactive substituents.

12. A coating composition comprising a thermosetting alkylated melamineformaldehyde resin, a compatible oil-modified alkyd resin and anitroaliphatic acid ester of phosphoric acid having only nitro andphosphoric catalytic reactive substituents.

13. A coating composition comprising a thermosetting alkylatedmelamine-formaldehyde resin, a compatible oil-modified alkyd resin and anitrobutyl acid ester of phosphoric acid having only nitro andphosphoric catalytic reactive substituents.

14. A coating composition comprising a dispersion of an alkylatedmelamine-formaldehyde resin, an oil modified alkyd resin dispersion and0.2 %-5% by weight of a nitroalip-hatic acid ester of phosphoric acidbased on the total weight of the resin dispersion, said ester havingonly nitro and phosphoric catalytic reactive substituents.

HERBERT J. WEST.

REFERENCES CITED UNITED STATES PATENTS Name Date West Oct. 17, 1950Number

1. A COATING COMPOSITION COMPRISING A THERMOSETTINGMELAMINE-FORMALDEHYDE RESIN AND A NITROALIPHATIC ACID ESTER OFPHOSPHORIC ACID HAVING ONLY NITRO AND PHOSPHORIC CATALYTIC REACTIVESUBSTITUENTS.